One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on the spaceship. Upon returning to the Earth, what is his own age and the age of the Earth-based twin brother?
A)20; 30
B)30; 50
C)40; 60
D)50; 70
E)70; 90

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The Answer of One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on the spaceship. Upon returning to the Earth, what is his own age and the age of the Earth-based twin brother?
A)20; 30
B)30; 50
C)40; 60
D)50; 70
E)70; 90

One 20-Year-Old Twin Brother Takes a Space Trip with a Speed